U.S. patent application number 14/661828 was filed with the patent office on 2016-06-09 for system and method for cooling a laser gain medium using an ultra-thin liquid thermal optical interface.
The applicant listed for this patent is Raytheon Company. Invention is credited to David M. Filgas, Christopher R. Koontz.
Application Number | 20160164241 14/661828 |
Document ID | / |
Family ID | 56095182 |
Filed Date | 2016-06-09 |
United States Patent
Application |
20160164241 |
Kind Code |
A1 |
Filgas; David M. ; et
al. |
June 9, 2016 |
SYSTEM AND METHOD FOR COOLING A LASER GAIN MEDIUM USING AN
ULTRA-THIN LIQUID THERMAL OPTICAL INTERFACE
Abstract
A heat sink for cooling a laser gain medium includes a coolant
channel, an inlet pore, an outlet pore, and a thermal optical
interface (TOI) channel. The coolant channel is configured to
receive a coolant for removing heat from the heat sink. The TOI
channel is coupled to the coolant channel by the inlet pore and the
outlet pore. The TOI channel is configured to receive a portion of
the coolant through the inlet pore. The received portion forms an
ultra-thin liquid TOI. The TOI channel is further configured to
return a portion of the TOI through the outlet pore to the coolant
channel.
Inventors: |
Filgas; David M.; (Newbury
Park, CA) ; Koontz; Christopher R.; (Manhattan Beach,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Raytheon Company |
Waltham |
MA |
US |
|
|
Family ID: |
56095182 |
Appl. No.: |
14/661828 |
Filed: |
March 18, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62089530 |
Dec 9, 2014 |
|
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|
Current U.S.
Class: |
372/35 |
Current CPC
Class: |
H01S 3/042 20130101;
H01S 3/0407 20130101; H01S 3/1643 20130101 |
International
Class: |
H01S 3/04 20060101
H01S003/04; H01S 3/042 20060101 H01S003/042 |
Claims
1. A heat sink for cooling a laser gain medium, the heat sink
comprising: a coolant channel configured to receive a coolant for
removing heat from the heat sink; an inlet pore; an outlet pore;
and a thermal optical interface (TOI) channel coupled to the
coolant channel by the inlet pore and the outlet pore, wherein: the
TOT channel is configured to receive at least a portion of the
coolant through the inlet pore, the received portion forms an
ultra-thin liquid TOI, the TOI channel is further configured to
return at least a portion of the TOI through the outlet pore to the
coolant channel, and the TOT channel is disposed between a surface
of the heat sink and a surface of the laser gain medium such that
the surface of the heat sink and the surface of the laser gain
medium form substantially parallel walls of the TOT channel.
2. The heat sink of claim 1, wherein the heat sink does not contact
the laser gain medium between the inlet port and the outlet
port.
3. The heat sink of claim 1, wherein the coolant and the TOI
comprise an optically transparent liquid.
4. The heat sink of claim 1, wherein the TOI channel comprises a
thickness of about 1-10 .mu.m.
5. The heat sink of claim 1, wherein the inlet pore comprises a
plurality of input pores and the outlet pore comprises a plurality
of output pores.
6. The heat sink of claim 1, wherein the heat sink further
comprises a plurality of lithographically-patterned shims that are
configured to define the TOI channel.
7. A system for cooling, the system comprising: a heat sink
comprising an inlet pore, an outlet pore, and a coolant channel
configured to receive a coolant for removing heat from the heat
sink; a thermal optical interface (TOI) channel coupled to the
coolant channel by the inlet pore and the outlet pore, wherein the
TOI channel is configured to receive at least a portion of the
coolant through the inlet pore, wherein the received portion forms
an ultra-thin liquid TOI, and wherein the TOI channel is further
configured to return at least a portion of the TOI through the
outlet pore to the coolant channel; and a laser gain medium
configured to generate heat energy and fluorescent energy, wherein
the TOI is configured to conduct the heat energy to the heat sink,
and wherein the TOI comprises an optically transparent liquid such
that the fluorescent energy is passed through the TOI to the heat
sink; wherein the TOI channel is disposed between a surface of the
heat sink and a surface of the laser gain medium such that the
surface of the heat sink and the surface of the laser gain medium
form substantially parallel walls of the TOI channel.
8. The system of claim 7, wherein the TOI channel is formed in the
heat sink.
9. The system of claim 7, wherein the TOI channel is formed in the
laser gain medium.
10. The system of claim 7, wherein the TOT channel comprises a
thickness of about 1-10 .mu.m.
11. The system of claim 7, wherein the laser gain medium comprises
a heat-dissipating portion and a non-heat-dissipating portion, and
wherein the heat sink comprises an upper heat sink and a lower heat
sink.
12. The system of claim 11, further comprising: a first side rail
coupled to a first side of the non-heat-dissipating portion of the
laser gain medium; and a second side rail coupled to a second side
of the non-heat-dissipating portion of the laser gain medium.
13. The system of claim 12, further comprising a seal configured to
hermetically seal the upper heat sink and the lower heat sink to
the laser gain medium through the non-heat-dissipating portion of
the laser gain medium and the first and second side rails.
14. A method for cooling a laser gain medium, the method
comprising: providing a coolant to a coolant channel of a heat
sink; allowing the coolant to leak through an inlet pore into a
thermal optical interface (TOI) channel to form an ultra-thin
liquid TOI; and allowing the TOT to leak through an outlet pore
back into the coolant channel; wherein the TOI channel is disposed
between a surface of the heat sink and a surface of the laser gain
medium such that the surface of the heat sink and the surface of
the laser gain medium form substantially parallel walls of the TOI
channel.
15. The method of claim 14, wherein the coolant and the TOI
comprise an optically transparent liquid.
16. The method of claim 14, wherein the TOI channel comprises a
thickness of about 1-10 .mu.m.
17. The method of claim 14, further comprising: conducting heat
energy generated by the laser gain medium through the TOI to the
heat sink; and allowing fluorescent energy generated by the laser
gain medium to pass through the TOI to the heat sink.
18. The method of claim 14, further comprising: coupling a first
side rail to a non-heat dissipating portion of the laser gain
medium; and coupling a second side rail to the non-heat dissipating
portion of the laser gain medium.
19. The method of claim 18, wherein the heat sink comprises an
upper heat sink and a lower heat sink, the method further
comprising coupling the upper and lower heat sinks to the laser
gain medium and the first and second side rails.
20. The method of claim 19, further comprising hermetically sealing
the upper and lower heat sinks to the laser gain medium through the
first and second side rails and the non-heat-dissipating portion of
the laser gain medium.
Description
CROSS-REFERENCE TO RELATED APPLICATION AND PRIORITY CLAIM
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application Ser. No.
62/089,530 filed on Dec. 9, 2014, which is hereby incorporated by
reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure is directed, in general, to high
power, solid-state laser gain amplifiers and, more specifically, to
a system and method for cooling a laser gain medium using an
ultra-thin liquid thermal optical interface.
BACKGROUND
[0003] High power, solid-state laser gain amplifiers can require
high performance cooling to dissipate waste heat fluxes over 100
W/cm.sup.2, while maintaining a low temperature rise between a
laser gain medium and a coolant. Typically, this high performance
cooling is achieved by flowing coolant directly over the gain
medium or by attaching to the gain medium a heat sink with internal
passages for flowing coolant. However, direct liquid cooling
generally requires very high coolant flow rates and pressure drops
to cool large heat fluxes. In addition, heat sinks are fabricated
from high thermal conductivity materials that may not be
well-matched in coefficient of thermal expansion (CTE) to the laser
gain medium, which can result in major performance issues, or from
CTE-matched material, which is difficult to fabricate microchannel
geometry and apply uniformly over large surface areas and results
in poorer thermal performance than non-CTE-matched heat sinks.
Finally, the use of a liquid metal or a solid material as a thermal
interface between the gain medium and a non-CTE-matched heat sink
has been considered. However, most of such liquid metals are toxic
and/or corrosive, and solid materials have a relatively low thermal
conductance, convert fluorescent energy into additional waste heat
at the gain medium interface, provide unacceptable uniformity
across the gain medium, and can generate stress due to CTE mismatch
with the gain medium.
SUMMARY
[0004] This disclosure provides a system and method for cooling a
laser gain medium using an ultra-thin liquid thermal optical
interface (TOI).
[0005] In one embodiment, a heat sink for cooling a laser gain
medium includes a coolant channel, an inlet pore, an outlet pore,
and a thermal optical interface (TOI) channel. The coolant channel
is configured to receive a coolant for removing heat from the heat
sink. The TOI channel is coupled to the coolant channel by the
inlet pore and the outlet pore. The TOI channel is configured to
receive a portion of the coolant through the inlet pore. The
received portion forms an ultra-thin liquid TOI. The TOI channel is
further configured to return a portion of the TOI through the
outlet pore to the coolant channel.
[0006] In another embodiment, a system for cooling includes a heat
sink, a TOI channel, and a laser gain medium. The heat sink
includes an inlet pore, an outlet pore, and a coolant channel that
is configured to receive a coolant for removing heat from the heat
sink. The TOT channel is coupled to the coolant channel by the
inlet pore and the outlet pore. The TOI channel is configured to
receive a portion of the coolant through the inlet pore. The
received portion forms an ultra-thin liquid TOI. The TOI channel is
further configured to return a portion of the TOT through the
outlet pore to the coolant channel. The laser gain medium is
configured to generate heat energy and fluorescent energy. The TOT
is configured to conduct the heat energy to the heat sink. The TOT
includes an optically transparent liquid such that the fluorescent
energy is passed through the TOI to the heat sink.
[0007] In yet another embodiment, a method for cooling a laser gain
medium includes providing a coolant to a coolant channel of a heat
sink. The coolant is allowed to leak through an inlet pore into a
TOI channel to form an ultra-thin liquid TOI. The TOT is allowed to
leak through an outlet pore back into the coolant channel.
[0008] Other technical features may be readily apparent to one
skilled in the art from the following figures, descriptions, and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] For a more complete understanding of the present disclosure,
reference is now made to the following description taken in
conjunction with the accompanying drawings, in which:
[0010] FIG. 1 illustrates a cross-sectional view of a portion of a
system for cooling a laser gain medium using an ultra-thin liquid
thermal optical interface (TOI) in accordance with an embodiment of
the present disclosure;
[0011] FIG. 2A illustrates a cross-sectional view of the heat sink
of FIG. 1 in accordance with an embodiment of the present
disclosure;
[0012] FIG. 2B illustrates a cross-sectional view of the laser gain
medium and heat sink of FIG. 1 in accordance with another
embodiment of the present disclosure;
[0013] FIG. 3 illustrates a front view of the system of FIG. 1 in
accordance with an embodiment of the present disclosure;
[0014] FIG. 4 illustrates a cross-sectional side view of the system
of FIG. 3 in accordance with an embodiment of the present
disclosure;
[0015] FIG. 5 illustrates a cross-sectional top view of the system
of FIGS. 3 and 4 in accordance with an embodiment of the present
disclosure; and
[0016] FIG. 6 is a flowchart illustrating a method for cooling a
laser gain medium using an ultra-thin liquid TOI in accordance with
an embodiment of the present disclosure.
DETAILED DESCRIPTION
[0017] FIGS. 1 through 6, discussed below, and the various
embodiments used to describe the principles of the present
disclosure in this patent document are by way of illustration only
and should not be construed in any way to limit the scope of the
disclosure. Those skilled in the art will understand that the
principles of the present disclosure may be implemented using any
number of techniques, whether currently known or not. Additionally,
the drawings are not necessarily drawn to scale.
[0018] FIG. 1 illustrates a cross-sectional view of a portion of a
system 100 for cooling a laser gain medium 102 using an ultra-thin
liquid thermal optical interface (TOI) 104 in accordance with an
embodiment of the present disclosure. The embodiment of the system
100 shown in FIG. 1 is for illustration only. Other embodiments of
the system 100 could be used without departing from the scope of
this disclosure.
[0019] Conventional high-power, solid-state laser gain amplifiers
generally use high performance cooling to dissipate waste heat
fluxes greater than 100 W/cm.sup.2, while maintaining a low
temperature rise between the gain medium and a coolant. High
performance cooling of a solid-state laser gain amplifier can be
also be achieved by flowing coolant directly over the gain medium
or by attaching to the gain medium a heat sink with internal
passages for flowing coolant. Direct liquid cooling can be applied
over large surface areas, but very high coolant flow rates and
pressure drops are typically required to cool heat fluxes greater
than 100 W/cm.sup.2 with a temperature difference of less than
10.degree. C. between the surface of the gain medium and the
coolant.
[0020] In the case of cooling with a heat sink, heat sinks capable
of dissipating the required heat flux with only a small temperature
rise and low coolant pressure drop can be fabricated from high
thermal conductivity materials, such as copper or diamond, but
these materials may not be well matched in coefficient of thermal
expansion (CTE) to the laser gain medium. A CTE mismatch between
the heat sink and gain medium creates major performance issues when
the cooled surface area is more than a few square centimeters, when
the assembly must tolerate wide temperature differences during
operation or storage, or when the process for attaching the heat
sink to the gain medium requires elevated temperatures. In these
cases, a relatively thick, compliant thermal interface material is
typically used, but such materials generally result in a large
temperature rise between the gain medium and coolant. Additionally,
such materials convert fluorescent energy into additional waste
heat at the gain medium interface.
[0021] Using a heat sink that is CTE-matched to the gain medium
enables the use of higher performance rigid bonding methods between
the gain medium and heat sink, such as soldering, but such methods
are very difficult to apply uniformly over large surface areas. The
thermal performance of CTE-matched heat sinks is much poorer than
for non-CTE-matched heat sinks, often due to the limitations with
manufacturing cooling channels in CTE-matched heat sinks. The use
of liquid metals as the thermal interface between the gain medium
and a non-CTE-matched heat sink has also been considered, but most
such materials are toxic and/or corrosive. Additionally, such
materials convert fluorescent energy into additional waste heat at
the gain medium interface.
[0022] In some situations, solid materials, such as graphite,
adhesives, gap pads, gaskets, greases or the like, are used for the
thermal interface. However, solid materials generally have a
relatively low thermal conductance, convert fluorescent energy into
additional waste heat at the gain medium interface, provide
unacceptable uniformity across the gain medium, and can generate
stress due to CTE mismatch with the gain medium. For example, some
conventional systems include a graphite thermal interface clamped
between the laser gain medium and the heat sink. This typically
requires compression of about 200 psi, which can create deformation
of the gain medium. In addition, a graphite thermal interface may
be unable to function efficiently with heat fluxes of greater than
150 W/cm.sup.2.
[0023] For the embodiment illustrated in FIG. 1, the system 100 for
cooling the laser gain medium 102 includes a heat sink 106 that may
be configured to provide the ultra-thin liquid TOT 104. For some
embodiments, the laser gain medium 102 may include Nd:YAG, Yb:YAG
or other suitable material configured to amplify a laser signal.
The laser gain medium 102 may generate power of up to hundreds of
W/cm.sup.2. This power may include sensible heat energy 108, along
with a substantial amount of fluorescent energy 110. The heat sink
106 may be a micro-channel-cooled heat sink. In addition, the heat
sink 106 may be fabricated from a high thermal conductivity
material, such as copper, diamond, aluminum, copper tungsten,
copper molybdenum, silicon carbide or the like.
[0024] For some embodiments, the laser gain medium 102 and/or the
heat sink 106 has lithographically-patterned features that allow
the laser gain medium 102 and the heat sink 106 to be mechanically
clamped together with a controlled gap thickness for the liquid of
the TOI 104, as described in more detail below. However, it will be
understood that the laser gain medium 102 may be coupled to the
heat sink 106 in any suitable manner.
[0025] The TOI 104 may include water, ethylene glycol, or other
suitable fluid and may be optically transparent to the pump and
laser wavelengths and scattered pump and signal light emitted from
the laser gain medium 102. Thus, as shown in FIG. 1, the TOI 104
may conduct the sensible heat energy 108 generated by the laser
gain medium 102 to the heat sink 106 (as opposed to using
convection or phase change on the heat energy 108 from the laser
gain medium 102), while the fluorescent energy 110 may pass through
the TOI 104 to the heat sink 106, where that energy 110 may be
absorbed directly by the heat sink 106. This embodiment prevents
the fluorescent energy 110 from heating the TOT 104, thereby
reducing the temperature differential between the laser gain medium
102 and the TOI 104 as compared to a system that includes a liquid
metal TOI.
[0026] The TOT 104 includes an ultra-thin layer of fluid between
the laser gain medium 102 and the heat sink 106. For example, for a
particular embodiment, the TOI 104 may be about 1-10 .mu.m thick.
Having such a micro-thickness for the TOT 104 provides a very low
thermal resistance, which creates a relatively high conductance
interface. This allows the heat energy 108 to be conducted through
the TOT 104, as described above. For a particular example, as
compared to conventional TOIs having a conductance of about 5
W/cm.sup.2-C, a 2-.mu.m thin film water TOI 104 may have a
conductance of about 30 W/cm.sup.2-C.
[0027] By having a liquid TOI 104 in contact with the laser gain
medium 102, high uniformity can be achieved, allowing the cooling
method provided by the system 100 to be easily scaled to
accommodate a laser gain medium 102 with a relatively large surface
area. In addition, a CTE-matched heat sink 106 is not needed
because the heat sink 106 does not have to be bonded to the laser
gain medium 102. Furthermore, a micro-channel-cooled heat sink 106
fabricated from a high thermal conductivity material, along with
the ultra-thin TOI 104 enables the system 100 to provide very high
cooling performance with modest coolant pressure drops. Therefore,
by providing an optically transparent, ultra-thin liquid TOI 104 as
a thermal interface to a high performance heat sink 106, the system
100 may be implemented as a high performance cooling system for
planar waveguide lasers and may support scaling the power of a
single planar waveguide to Megawatt (MW) average power levels.
[0028] Although FIG. 1 illustrates one example of a system 100 for
cooling a laser gain medium 102, various changes may be made to the
embodiment shown in FIG. 1. For example, the makeup and arrangement
of the system 100 are for illustration only. Components could be
added, omitted, combined, subdivided, or placed in any other
suitable configuration according to particular needs.
[0029] FIG. 2A illustrates a cross-sectional view of the heat sink
106 in accordance with an embodiment of the present disclosure. The
embodiment of the heat sink 106 shown in FIG. 2A is for
illustration only. Other embodiments of the heat sink 106 could be
used without departing from the scope of this disclosure.
[0030] For the illustrated embodiment, the heat sink 106, which is
fabricated from a high thermal conductivity material, such as
copper, diamond or the like, includes a coolant channel 112 through
which a coolant (not shown in FIG. 2A) may flow. The coolant may
include water, ethylene glycol or the like. The heat sink 106 also
includes supply and return ports (not shown) to allow a continuous
stream of the coolant to flow through the heat sink 106 and remove
heat from the system 100.
[0031] In addition, the heat sink 106 includes a TOI channel 114
through which the TOI 104 (not shown) may flow. The TOI channel 114
is formed by shims 116, which form edges that define the TOI
channel 114. The heat sink 106 may also include additional shims
(not shown) distributed substantially evenly across the surface of
the heat sink 106 to provide additional support for a consistent
gap thickness. For some embodiments, these additional shims may be
cylindrical in shape. The heat sink 106 also includes at least one
inlet pore 118 and at least one outlet pore 120. However, the heat
sink 106 may include any suitable number of inlet pores 118 and
outlet pores 120. For some embodiments, the shims 116 (and, thus,
the TOI channel 114) and the pores 118 and 120 may be
lithographically-patterned into the heat sink 106. As they define
the TOI channel 114, the shims 116 have a height corresponding to
the desired thickness of the TOI 104. Thus, for some embodiments,
the shims 116 may have a height between about 1 and about 10
.mu.m.
[0032] The liquid that makes up the TOI 104, which is the same
liquid as a coolant flowing through the heat sink 106, is provided
with a supply and return (i.e., the pores 118 and 120) having a
sufficient flow rate to remove any bubbles trapped between the
laser gain medium 102 and the heat sink 106. The inlet pore 118 is
configured to allow the coolant flowing through the coolant channel
112 to leak into the TOI channel 114 where the coolant forms the
ultra-thin liquid TOI 104. The outlet pore 120 is configured to
allow the TOI 104 to leak out of the TOI channel 114 and back into
the coolant channel 112. A natural pressure differential causes the
coolant to leak into the TOI channel 114 and the TOI 104 to leak
out of the TOI channel 114.
[0033] The TOI 104 is quasi-static in that its flow rate is very
slow; however, the flow rate is not zero. The flow rate of the
coolant through the coolant channel 112 is extremely fast as
compared to the flow rate of the TOI 104 through the TOT channel
114. For a particular example, the flow rate of the coolant may be
about 10 gallons/min., while the flow rate of the TOI 104 may be
about 0.5 ml/min. Thus, for this example, less than 1% of the
coolant is supplied through the inlet pore 118 to the TOI channel
104. The flow rate through the TOI channel 114 may be controlled
by, among other factors, the number and size of the pores 118 and
120. Also, although not shown in FIG. 2A, it will be understood
that a fluid seal is provided around the perimeter of the heat sink
106 to prevent the TOI 104 from leaking out of the TOI channel 114
other than through the outlet pore 120.
[0034] Although FIG. 2A illustrates one example of a heat sink 106
for cooling a laser gain medium 102, various changes may be made to
the embodiment shown in FIG. 2A. For example, the makeup and
arrangement of the heat sink 106 are for illustration only.
Components could be added, omitted, combined, subdivided, or placed
in any other suitable configuration according to particular
needs.
[0035] FIG. 2B illustrates a cross-sectional view of the laser gain
medium 102 and the heat sink 106 in accordance with another
embodiment of the present disclosure. The embodiments of the laser
gain medium 102 and the heat sink 106 shown in FIG. 2B are for
illustration only. Other embodiments of the laser gain medium 102
and the heat sink 106 could be used without departing from the
scope of this disclosure.
[0036] For the embodiment illustrated in FIG. 2B, the TOI channel
114 is formed in the laser gain medium 102 instead of in the heat
sink 106. Thus, the laser gain medium 102 may be
lithographically-patterned to form the shims 116 that define the
TOI channel 114. The heat sink 106 may still include the inlet and
outlet pores 118 and 120. For this embodiment, when the heat sink
106 is coupled to the laser gain medium 102, the pores 118 and 120
couple the coolant channel 112 of the heat sink 106 to the TOI
channel 114 of the laser gain medium 102. Cooling of the laser gain
medium 102 in this embodiment is provided in the same manner as
described above with reference to FIG. 2A.
[0037] Although FIG. 2B illustrates one example of a laser gain
medium 102 and heat sink 106, various changes may be made to the
embodiment shown in FIG. 2B. For example, the makeup and
arrangement of the laser gain medium 102 and the heat sink 106 are
for illustration only. Components could be added, omitted,
combined, subdivided, or placed in any other suitable configuration
according to particular needs. For a particular example, the TOI
channel 114 may be included partially in the laser gain medium 102,
as shown in FIG. 2B, and partially in the heat sink 106 as shown in
FIG. 2A.
[0038] FIGS. 3 through 5, below, provide various views of the
system 100 in accordance with an embodiment of the present
disclosure. These views are illustrated and described based on the
heat sink 106 of FIG. 2A. However, it will be understood that a
corresponding system 100 could be implemented using the alternate
configuration of the laser gain medium 102 and the heat sink 106
illustrated in FIG. 2B, as well as any other suitable
configurations of the laser gain medium 102 and/or the heat sink
106.
[0039] FIG. 3 illustrates a front view of the system 100 in
accordance with an embodiment of the present disclosure. The
embodiment of the system 100 shown in FIG. 3 is for illustration
only. Other embodiments of the system 100 could be used without
departing from the scope of this disclosure.
[0040] The illustrated system 100 includes the heat sink 106, which
in this embodiment includes an upper heat sink 106a and a lower
heat sink 106b. The upper and lower heat sinks 106a and 106b are
mirror images of each other. The heat sink 106 is coupled to the
laser gain medium 102, which includes a heat-dissipating portion
(not shown in FIG. 3) and a non-heat dissipating portion 132, as
described in more detail below in connection with FIG. 5. The
system 100 also includes side rails 134a and 134b. As described in
more detail in connection with FIG. 5, the side rails 134a and 134b
are coupled along at least a portion of the length of the laser
gain medium 102 by a coupling medium 136, such as an adhesive,
solder, silicate bonding, oxide bonding or the like.
[0041] Although FIG. 3 illustrates one example of a front view of
the system 100, various changes may be made to the embodiment shown
in FIG. 3. For example, the makeup and arrangement of the system
100 are for illustration only. Components could be added, omitted,
combined, subdivided, or placed in any other suitable configuration
according to particular needs.
[0042] FIG. 4 illustrates a cross-sectional side view of the system
100 in accordance with an embodiment of the present disclosure. The
embodiment of the system 100 shown in FIG. 4 is for illustration
only. Other embodiments of the system 100 could be used without
departing from the scope of this disclosure. The view shown in FIG.
4 illustrates an inner section of the system 100, not the entire
length of the system 100, as shown in FIG. 5.
[0043] The illustrated system 100 includes the laser gain medium
102 and the upper and lower heat sinks 106a and 106b. During
operation, for the upper heat sink 106a, for example, the coolant
channel 112a of the heat sink 106a includes coolant 140, which
leaks from the coolant channel 112a through the inlet pore 118a
into the TOI channel 114a and forms the TOI 104. The TOI 104 leaks
from the TOI channel 114a through the outlet pore 120a back into
the coolant channel 112a. Thus, the TOT 104 is continuously
refreshed.
[0044] The system 100 of FIG. 4 also includes an optional stiffener
142 (not shown in connection with FIG. 3). The stiffener 142, which
is configured to provide structural support to the system 100, may
include copper tungsten, copper molybdenum or the like or may
include an optically transparent material such as YAG or the like.
For embodiments in which the stiffener 142 is implemented, the
material of the stiffener 142 may be CTE-matched to the laser gain
medium 102. Also, an additional TOI, formed from an adhesive or
other suitable TOI, may be included between the laser gain medium
102 and the stiffener 142 (not shown in FIG. 4).
[0045] Although FIG. 4 illustrates one example of a side view of
the system 100, various changes may be made to the embodiment shown
in FIG. 4. For example, the makeup and arrangement of the system
100 are for illustration only. Components could be added, omitted,
combined, subdivided, or placed in any other suitable configuration
according to particular needs.
[0046] FIG. 5 illustrates a cross-sectional top view of the system
100 in accordance with an embodiment of the present disclosure. The
embodiment of the system 100 shown in FIG. 5 is for illustration
only. Other embodiments of the system 100 could be used without
departing from the scope of this disclosure.
[0047] For the illustrated embodiment, the laser gain medium 102
includes the heat-dissipating portion 138 and the
non-heat-dissipating portion 132a and 132b. Although illustrated
separately, these portions 138 and 132a-b may form a single,
continuous laser gain medium 102 with differing properties (i.e.,
heat-dissipating or non-heat-dissipating) based on the location of
each portion 138 and 132a-b within the system 100. For a particular
example, the laser gain medium 102 may have a top surface area of
about 20-30 cm long by about 3 cm wide.
[0048] The illustrated system 100 also includes a side rail 134a or
134b on each side of the laser gain medium 102. The side rails 134a
and 134b may be coupled to the non-heat-dissipating portions 132a
and 132b of the laser gain medium 102 by a coupling medium 136,
such as adhesive, solder or the like. Each side rail 134a and 134b
is also coupled to a corresponding TOI channel 114a and 114b, which
is in turn coupled to the heat-dissipating portion 138 of the laser
gain medium 102.
[0049] The system 100 also includes a seal 150, such as an O-ring,
silicate bond or adhesive, that is configured to hermetically seal
the system 100 to prevent the TOI 104 from exiting the TOI channel
114 in a location other than the outlet pore 120. The seal 150 is
included along the length of the side rails 134a and 134b, as well
as through the non-heat-dissipating portions 132a and 132b of the
laser gain medium 102 and the coupling media 136. Thus, the side
rails 134a and 134b are configured to prevent the seal 150 from
contacting the heat-dissipating portion 138 of the laser gain
medium 102.
[0050] Although FIG. 5 illustrates one example of a top view of the
system 100, various changes may be made to the embodiment shown in
FIG. 5. For example, the makeup and arrangement of the system 100
are for illustration only. Components could be added, omitted,
combined, subdivided, or placed in any other suitable configuration
according to particular needs.
[0051] FIG. 6 is a flowchart illustrating a method 200 for cooling
a laser gain medium 102 using an ultra-thin liquid TOI 104 in
accordance with an embodiment of the present disclosure. The method
200 shown in FIG. 6 is for illustration only. Cooling the laser
gain medium 102 using the TOI 104 may be performed in any other
suitable manner without departing from the scope of this
disclosure.
[0052] Initially, side rails 134 are coupled to a laser gain medium
102 (step 202). As a particular example, in some embodiments, a
side rail 134a or 134b may be coupled to each side of a laser gain
medium 102 that includes a heat-dissipating portion 138 and a
non-heat-dissipating portion 132a and 132b. The side rails 134a and
134b may be coupled to the non-heat dissipating portion 132a and
132b through coupling media 136 and to the heat-dissipating portion
138 through the TOI channels 114a and 114b. A heat sink 106 is
coupled to the laser gain medium 102 and the side rails 134 (step
204). As a particular example, in some embodiments, an upper heat
sink 106a and a lower heat sink 106b may be mechanically clamped to
the laser gain medium 102 and side rails 134a and 134b. For some
embodiments, a stiffener 142 may be coupled between the upper heat
sink 106a and the laser gain medium 102.
[0053] The heat sink 106 is hermetically sealed to the laser gain
medium 102 through the side rails 134 (step 206). As a particular
example, in some embodiments, the upper heat sink 106a and the
lower heat sink 106b are hermetically sealed to the
non-heat-dissipating portion 132a and 132b of the laser gain medium
102, while the seal 150 along the length of the heat-dissipating
portion 138 of the laser gain medium 102 is provided through the
side rails 134a and 134b instead of directly through that portion
138 of the laser gain medium 102.
[0054] Coolant 140 is provided to a coolant channel 112 of the heat
sink 106 (step 208). As a particular example, in some embodiments,
the coolant 140 is introduced into the coolant channel 112 through
a supply, where the coolant 140 may flow through the heat sink 106
and then remove heat by exiting the heat sink 106 through a return.
For some embodiments, the coolant 140 may include water, ethylene
glycol or other fluid that is optically transparent to fluorescent
energy 110.
[0055] The coolant 140 in the coolant channel 112 is allowed to
leak through one or more inlet pores 118 into a TOI channel 114 to
form the ultra-thin liquid TOI 104 (step 210). As a particular
example, in some embodiments, the TOI channel 114 may be about 1-10
.mu.m thick, resulting in an ultra-thin TOI 104 that provides a
very low thermal resistance and, thus, a relatively high
conductance interface. The TOI 104 is allowed to leak through one
or more outlet pores 120 back into the coolant channel 112 (step
212). Together with the inlet pores 118, the outlet pores 120 allow
the TOI 104 to be slowly refreshed, resulting in a quasi-static
liquid TOI 104.
[0056] Heat energy 108 is conducted from the laser gain medium 102
to the heat sink 106 through the TOI 104 (step 214). Because of the
relatively high conductance interface of the TOI 104, the TOI 104
can conduct the heat energy 108 to the heat sink 106 relatively
efficiently. However, fluorescent energy 110 emitted from the laser
gain medium 102 is allowed to pass through the TOI 104 to the heat
sink 106 (step 216).
[0057] In this way, the fluorescent energy 110 from the laser gain
medium 102 does not create hot spots on the laser gain medium 102,
which can create performance issues, and the temperature rise from
the laser gain medium 102 to the heat sink 106 is significantly
reduced as compared to a system having a solid TOI or other TOI
that is not optically transparent to the fluorescent energy 110.
Furthermore, because the TOI 104 is liquid, contact between the TOI
104 and the laser gain medium 102 is uniform even across a large
surface area. Finally, the system 100 may be implemented as a high
performance cooling system for planar waveguide lasers and may
support scaling the power of a single planar waveguide to MW
average power levels by implementing the optically transparent,
ultra-thin liquid TOI 104 as a thermal interface to the high
performance heat sink 106.
[0058] Although FIG. 6 illustrates one example of a method 200 for
cooling a laser gain medium 102 using an ultra-thin liquid TOI 104,
various changes may be made to the embodiment shown in FIG. 6. For
example, while shown as a series of steps, various steps in FIG. 6
could overlap, occur in parallel, occur in a different order, or
occur multiple times.
[0059] Modifications, additions, or omissions may be made to the
apparatuses and methods described here without departing from the
scope of the disclosure. For example, the components of the
apparatuses may be integrated or separated. The methods may include
more, fewer, or other steps. Additionally, as described above,
steps may be performed in any suitable order.
[0060] It may be advantageous to set forth definitions of certain
words and phrases used throughout this patent document. The term
"couple" and its derivatives refer to any direct or indirect
communication between two or more elements, whether or not those
elements are in physical contact with one another. The terms
"include" and "comprise," as well as derivatives thereof, mean
inclusion without limitation. The term "or" is inclusive, meaning
and/or. The term "each" refers to each member of a set or each
member of a subset of a set. Terms such as "over" and "under" may
refer to relative positions in the figures and do not denote
required orientations during manufacturing or use. Terms such as
"higher" and "lower" denote relative values and are not meant to
imply specific values or ranges of values. The phrases "associated
with" and "associated therewith," as well as derivatives thereof,
may mean to include, be included within, interconnect with,
contain, be contained within, connect to or with, couple to or
with, be communicable with, cooperate with, interleave, juxtapose,
be proximate to, be bound to or with, have, have a property of, or
the like.
[0061] While this disclosure has described certain embodiments and
generally associated methods, alterations and permutations of these
embodiments and methods will be apparent to those skilled in the
art. Accordingly, the above description of example embodiments does
not define or constrain this disclosure. Other changes,
substitutions, and alterations are also possible without departing
from the spirit and scope of this disclosure, as defined by the
following claims.
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